Filter a specific value as well as allow user entery selection

Does anyone know if you can create a default value selection to always be used in a query, and allow a user to enter values as a variable?

For example, say I want to see employees for Department 1 in every Webi report using this query (can't use a variant) but I want the managers to be able to add their own Department (2-5) to the report.

What is the best practice for achieving this goal?

Thanks.